This proposal describes a 5-year training program to develop an academic career in Clinical Pathology and Microbiology. The proposed research will investigate the mucosal inflammatory response to bacterial iron metabolism. In response to diverse bacteria, the respiratory mucosa secretes siderocalin (lipocalin2), a small protein that binds the bacterial iron scavenging molecule enterobactin. Siderocalin sequesters iron from bacteria, and can prevent replication of enterobactin-dependent bacteria. In cell culture,1 siderocalin bound to enterobactin causes release of the chemokine IL-8, suggesting it has additional pro-inflammatory effects. This research plan will test the hypothesis that siderocalin mediates a mucosal inflammatory response, based on the iron-status of its bound enterobactin, through the followingaims: 1) Determine if siderocalin mediates a mucosal inflammatory response to bacteria in vivo. The PI will use animal models of nasal colonization and pneumonia,siderocalin knockout mice and isogenic Klebisiella pneumoniae enterobactin mutants to measure the effects of siderocalin on bacterial growth, chemokine production and neutrophil recriutment. 2) Identify the cellular components required for chemokine release in response to siderocalin in vitro. The PI will use a cell culture model to determine the requirement for the siderocalin receptor and chemokine regulatory proteins to respond to siderocalin. The principal investigator, Michael Bachman M.D. Ph.D., has completed his residency in Clinical Pathology at the Hospital of the Universityof Pennsylvania. He is expanding his reseach skills to include innate immunity to bacterial pathogens and focusing his career on medical microbiology. His advisor is Jeffrey Weiser M.D., an expert in the host response to bacterial colonization. To harness additional expertise, he has established a scientific advisory committee composed of Robert Wilson M.D. Ph.D.(human iron metabolism), David Artis Ph.D. (mucosal immunity) and Michael May (signal transduction). The faculty and facilities make the University of Pennsylvania an ideal environment in which to complete this training program.